Portion of a motorcycle seat



FIG. 1 is a perspective view of a portion of a motorcycle seat showing our new design, the broken lines are shown for illustrative purposes only and form no part of the claimed design;

FIG. 2 is a top plan view thereof; and,

FIG. 3 is a right side elevational view thereof.

The front, bottom, rear and left side views of the design are not visible in their normal intended use. 

The ornamental design for a portion of a motorcycle seat, as shown and described. 